IMEI doesn’t match phone number??

I have an iPhone 7 Plus and an iPhone 8 that I have been trying to unlock. The unlock portal repeatedly says that the IMEI does not match the phone number provided. I have double-checked the IMEI and confirmed with ATT store staff, and they do match. Both phones are paid off, not under contract, and with no commitments. I have $0 outstanding account balance. I cannot figure out what else to do, and none of the customer service representatives I have spoken with have done anything other than create a ticket and told me to wait 2-5 days. I am hoping someone has a solution for me!